Filter device

ABSTRACT

A filter device for separating water and other impurities from liquid fuel including a housing body ( 11 ), inside which a first filter element ( 12 ) is disposed; a collector vessel ( 17 ) which is disposed underneath the filter element ( 12 ); a pump ( 25 ) which is used to remove water present in the collector vessel ( 17 ), and a detector ( 23 ) which is used to determine whether water has accumulated in the collector vessel ( 17 ).

BACKGROUND OF THE INVENTION

The invention relates to a filter device for separating water and otherimpurities from liquid fuels with a housing body having a first filterelement disposed in its interior and a water collecting vessel disposedunderneath the filter element.

DE 33 06 294 C2 discloses a filter device, which is used to separatewater and other impurities from liquid fuels, particularly to separatewater and solid particles contained in diesel fuels. The known filterdevice comprises a housing body in the interior of which a first and asecond filter element are arranged. A collector basin is disposedunderneath these filter elements. This collector basin has two separateareas for collecting and discharging the impurities and the water. Atthe lower end, the system is provided with a drain plug. As soon as theremoved water has reached a certain amount, the drain plug must bemanually opened and the water discharged from the filter device. This istime-consuming; moreover, manual removal of the water is reliable onlyif an operator checks the entire device at regular intervals.

SUMMARY OF THE INVENTION

The object of the invention is to avoid the aforementioned disadvantagesand to provide a filter device for separating water and other impuritiesfrom liquid fuels, which provides reliably purified fuel withoutrequiring manual maintenance.

This object is attained by the invention as described and claimedhereinafter.

The substantial advantage of the invention is that an automatic waterdischarge mechanism is provided in the filter device. This ensuresnearly maintenance free operation. Only replacing the filter elementrequires manual intervention in the system.

According to one embodiment of the invention, the pump works in suctionoperation or pressure operation, i.e., for suction operation it isdisposed in the water discharge line. For pressure operation it isdisposed in the fuel intake line and thus generates a positive pressurein the filter device, which is relieved by opening a valve in the waterdischarge line. The water flows out due to the positive pressure withinthe filter device.

To prevent problems at extremely low temperatures, the filter device isprovided with a heating element. This can be a heat exchanger which issupplied with a heat transfer medium. It is also possible to arrange anelectrical heating unit in the system, which is actuated when thetemperature falls below a certain level. Instead of a heating element,the fuel return flow may be used to heat the fuel. Due to the heat ofthe engine, the return flow typically has a higher temperature than thefuel coming from the tank. This heated fuel may be supplied to thefilter device via a thermostat valve.

The filter device can comprise two filter systems. The first filter is aprefilter, the second a downstream main filter. The two filter systemscan be constructed identically and be linked by corresponding adapterelements.

To monitor the performance of the filters, it is possible in accordancewith a further embodiment of the invention to utilize pressure sensors.A pressure sensor can measure, for instance, the differential pressurebetween intake line and discharge line and signal that the filter needsmaintenance when the differential pressure exceeds a certain thresholdvalue. If the fuel is supplied to the filter device at a definedpressure, a sensor is required only in the discharge line. Based on themeasurement signal of the sensor, a pressure difference caused by thefilter device can be determined and displayed.

If the fuel system has been emptied, the system has to be refilled witha corresponding pump. This pump can for instance be a manually operatedpump for venting.

Typically, the filter devices according to the invention are used intrucks, construction machines and the like. To prevent the transfer ofvibrations and shocks of the machine to the filter system, a furtherembodiment of the invention provides for vibration decoupling andarrangement of the filter device on a support structure withcorresponding decoupling elements.

These and other features of further preferred embodiments of theinvention are set forth in the claims as well as in the description andthe drawings. The individual features may be implemented either alone orin combination in the embodiment of the invention or in other fields ofapplication and may represent advantageous embodiments that areprotectable per se, for which protection is hereby claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference toworking embodiments.

FIG. 1 shows a schematic representation of a filter system,

FIG. 2 shows a further variant of a filter system,

FIG. 3 shows a sectional view of a mechanically detailed filter system,

FIG. 4 is a variant of the schematic structure shown in FIG. 2, and

FIG. 5 is a schematic representation of the venting of the two filters.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The filter system according to FIG. 1 comprises a prefilter 10 with afilter housing 11. The filter housing contains a filter element 12. Thefluid to be filtered is supplied from a tank 13 via line 14 to a firstintake line 15 for prefilter 10. There the fuel enters the contaminatedfluid area 16. Any water contained therein settles out in waterreservoir 17. The fuel flows through filter element 12 and leavesprefilter 10 purified via clean fluid area 18 and discharge line 19. Viadischarge line 19 the fuel reaches a fluid pump 20 where it is highlycompressed and guided through a main filter 21 to the injection valves(not shown) of an internal combustion engine. The excess fuel isreturned to the tank via line 22.

In prefilter 10 a water sensor 23 is provided. At an appropriately highwater level in the water reservoir 17, the water sensor generates asignal that causes the water to be pumped away via a two-way valve 24 bymeans of pump 25 and to be supplied via the two-way valve to a waterdischarge vessel 27. To remove the residual water in pump 25 and thevarious valves 24, 26, the valves are switched. Actuating pump 25 causesfuel to be supplied to the pump via line 28. Due to the switched valve26, this fuel is supplied via a second feed line 29 to the prefilter 10.

FIG. 2 shows a filter system with a prefilter 10 and a main filter 21.Fuel is supplied to prefilter 10 via line 30 and pump 31 as well aspressure relief valve 32. In prefilter 10 there is again a sensor 33 todetect any water that has collected on the bottom of the prefilter and adischarge line 34. If the amount of water exceeds a certain measuredvalue, the sensor causes the two-way valve 35 to be opened. Due to thepump pressure of pump 31 the water flows to the water discharge viadischarge line 34 and two-way valve 35.

The filtered fuel passes via line 36 and fluid pump 20 to the mainfilter 21, where it is purified and then leaves the main filter and thefilter system via line 37. From there the fuel is conveyed to theindividual injector nozzles of an internal combustion engine. The excessfuel is returned via line 38 of fluid pump 20.

To heat the prefilter 10, the excess fuel, which is supplied via line 38to fluid pump 20, can be diverted there and be provided to the prefiltervia line 39 and a thermostat valve 40 in order to heat the fuelcontained in the prefilter. If the thermostat valve does not switch overtoward prefilter 10, the heated fuel flows via line 41 directly intosupply tank 42.

FIG. 3 shows a detailed sectional view of the individual components of acompact system in which both a prefilter and a main filter are provided.As the drawing shows, the two filters are identically constructed. Thisresults in a significant reduction in the manufacturing cost. Bothfilters comprise a filter housing 11, each with a filter element 12therein and a support tube 43. In the prefilter 10 there is also a watersensor 44. The filter housings are directly attached to a filter carrier45 and can be removed to replace the filter element. The filter carrierincludes three sensors. Sensor 46 detects the fuel pressure after theprefilter, sensor 47 the fuel pressure in front of the main filter, andsensor 48 the fuel pressure after the main filter.

Pump 49 for dewatering the prefilter is disposed at the side of theprefilter. In the area of the pump, water outlet 50 is provided. Alsovisible on the filter carrier are the fluid inlet 51 and fluid outlet52. It is of course also possible to integrate certain mechanicalcomponents in the filter carrier through lines in the filter carrier.

The filter carrier is provided with vibration-decoupling mountingelements 53, 54. These can, for instance, be rubber elastic elementsfixed to a mounting structure by means of a screwed connection.

At the prefilter disposed on the right side, the purified fluid isdirected outwardly via connection 56 and is supplied via a line (notshown) to the main filter disposed on the left side. The fluid purifiedin the main filter passes to the fuel injection pump via connection 57.

FIG. 4 shows a variant of the schematic structure depicted in FIG. 2.The significant difference from the structure of FIG. 2 is that only twopumps are required for filling the entire system, emptying both filtersand dewatering the prefilter 10. These are pumps 31 and 58.

The pump 31 pumps the fuel from tank 42 both into the prefilter and vialine 59 also into the main filter 21. A valve 60 and a non-return valve61 are installed in line 59. Above the switching valve 62, which is atwo-way valve, there is a line 63 leading to tank 42 and a line 64leading to a water collector vessel 65. Above and below valve 62,sensors 66, 67 are installed in the line. These sensors generateactuating signals for valve 62.

When the system is initially filled, pump 31 is actuated. Pump 31 fillsthe main filter 21 via line 59 and non-return valve 61 and the prefilter10 via line 68. If valve 60 can be opened when main filter 21 is beingfilled, the non-return valve 61 is not required. It merely represents analternative embodiment. To remove any water that may have accumulated inthe prefilter 10, pump 58 is actuated. Initially the fluid flows throughline 63 into tank 42. As soon as water impinges on one of the twosensors 66, 67, the corresponding sensor switches valve 62 so that thewater is subsequently discharged via line 64 into the water collectorvessel 65. As soon as fuel impinges on sensor 67, it switches valve 62back to the position shown. After a certain predefined time, pump 58 isturned off.

When the filter elements are replaced, the filters must be emptied. Forthis purpose, valve 60 is opened. With the aid of pump 58, bothprefilter 10 and main filter 21 can now be emptied via line 63.

Pumps 58 and 31 can advantageously be arranged in a common pump module.This has the advantage that the connections are placed within the moduleso that no external lines are required.

FIG. 5 shows a schematic illustration of the venting of the two filters10 and 21. During filling, the air escaping from the enclosed structuresflows via line 69 and line 70 into a venting block 71 and from there viaa throttle point 72 and line 73 into the fuel tank 42. The escaping airlifts the non-return valve of filter 21, which consists of a ball 74, inupward direction where the ball does not seal an orifice but is merelyheld. As soon as the system is filled, a suction pump creates a negativepressure in prefilter 21 so that ball 74 moves downwardly and seals theventing opening. In the main filter 21 there is positive pressure. As aresult, a small amount of fuel escapes via line 69 and throttle point 72so that no air cushion can build up in the main filter.

What is claimed is:
 1. A filter device for separating water and otherimpurities from a liquid fuel, the filter device comprising: a firstfilter including a housing body, a filter element disposed in theinterior of said housing body, and a water collector vessel disposedbelow the filter element; a pump for removing water from said watercollector vessel; and a sensor for detecting water accumulated in saidcollecting vessel, wherein said pump is actuated in response todetection by said sensor of an accumulation of water in said collectorvessel, and wherein said pump is disposed on a fuel supply line leadingto said first filter and works in pressure operation.
 2. A filter deviceaccording to claim 1, further comprising a heating element in thehousing body.
 3. A filter device according to claim 1, furthercomprising a connection for supplying heated fuel to the first filter toheat the first filter.
 4. A filter device according to claim 1, furthercomprising a second filter downstream of said first filter.
 5. A filterdevice according to claim 4, wherein said second filter has an identicalstructure to said first filter.
 6. A filter device according to claim 4,further comprising a first pressure sensor in a fuel supply line leadingto said second filter and a second pressure sensor in a fuel dischargeline leading from said second filter for determining fuel pressureupstream and downstream of said second filter.
 7. A filter deviceaccording to claim 6, further comprising a third pressure sensor in anoutlet line from said first filter for detecting the outlet pressure offuel from said first filter.
 8. A filter device according to claim 7,wherein the pressure sensors are arranged together in a sensor system.9. A filter device according to claim 4, further comprising a manuallyoperable pump for venting at least one of the first and second filters.10. A filter device according to claim 1, wherein said filter device ismounted on a support structure via decoupling elements so that thefilter device is vibration-decoupled from the support structure.